1. Field of the Invention
This invention relates to a process and to apparatus for the acid-catalyzed hydrolysis of fatty acid glycerides.
2. Statement of Related Art
Processes are known to the art for the hydrolysis of fatty acid glycerides with water to fatty acids and glycerol. At the present time the typical commercial process is mainly carried out in the absence of a catalyst under pressures of from 20 to 60 bar and at temperatures in the range of from 150.degree. to 260.degree. C., and is therefore energy-intensive.
The reaction velocity can be increased by alkaline and acidic catalysts. However, the pressureless hydrolysis of glycerides is only possible with acidic catalysts by the so-called Twitchell process (Ullmann's Enzyklopadie der technischen Chemie, 4th Edition, Vol. 11, page 529, last paragraph). The acidic catalysts used for this process consist of aromatic sulfonic acids. Although the process can be carried out in the absence of pressure at temperatures of the order of 100.degree. C., this does require very long reaction times of more than 20 hours. In addition, no continuous version of the process is known.
According to N.O.V. Sonntag in J. Am. Oil Chemists' Soc., 1979, 729 A, the Twitchell process is carried out in batches in three or four successive steps. Fresh water containing the catalyst is added in each step. The following times and yields are obtained, for example, in a four-step Twitchell process:
in the first step, 18 hours and 60%, PA1 in the second step, 12 hours and 25%, PA1 in the third step, 6 hours and 10% and PA1 in the fourth step, 4 hours and 5%. PA1 in the first step, 20 to 24 hours and 75%, PA1 in the second step, 12 hours and 15% and PA1 in the third step, 4 hours and 5%.
The following times and yields are obtained in a three-step process:
In another known acid-catalyzed process, hydrolysis is carried out in batches on an industrial scale in two stages. The yield is only 88-90%.
In the known processes, the degree of hydrolysis is never better than 95% except in cases of very long reaction times or a very large number of steps with increasingly lower concentrations of glycerol. For this reason, these known processes are also energy-intensive.